Web coating apparatus



1951 D. A. NEWMAN WEB COATING APPARATUS Filed July 10, 1947 w 6 mm M W m KM KT m M A S M) M w D i atented Aug. 21, 1951 WEB COATING APPARATUS Douglas A. Newman, Sea Cliff, N. Y., assignor to Columbia Ribbon and Carbon Manufacturing Company, Inc., Glen Cove, N. Y., a corporation of New York Application July 10, 1947, Serial No. 760,133

5 Claims. 1

This invention relates to the applying of continuous coatings such as wax-base transfer ink or other coating materials to a continuous web of paper or the like for use as transfer strips for manifolding or duplication uses.

An object of the invention is to provide an improved method and apparatus for app y a continuous ink or other coating, which may be relatively thick or quick-drying or both, to a continuous web of paper or the like whereby the coating has a high degree of uniformity, as tested on sections taken from the starting and end portions of the web, at the beginning and end respectively of an extended run.

A further object of the invention is to provide an improved apparatus as above which is reliable in operation, and is extremely simple and easy to manufacture and operate.

Heretofore uniform and satisfactory coatings of ink and the like have been applied to a con- .tinuous web by passing the web over a ductor roller which dips into a tank carrying the coating substance, so as to provide on the roller a thin film of the substance in a quantity genercame non-uniform. In overcoming this track- 1 ing or gathering of the coating substance on the Li web, an equalizer or doctor blade was employed which scraped the web and coating, and removed the excess coating substance, returning it to the tank. While this provided an excellent and smooth coating of uniform thickness, eliminating the tracking or gathering of thefcoating substance, the uniformity of the coating was not maintained throughout an extended nm. .,,,-The reason for this was that (1) the coated P'poruon of the web between the applic roller and the doctor blade was of fairly substantial length, (2) the coating substance contains certain filterable ingredients, (3) the paper web being coated is normally rather absorptive in character, and during the travel of the web from the roller to the blade the vehicle of the coating substance was absorbed by the web and penetrated the latter, with the result that the filterable ink solids i. e. undissolved dyes, pigments,

and waxes remaining on the web surface were in a higher concentration than those of the coating substance in the tank. This higher concentration of ink solids was scraped off by the doctor blade and returned to the tank, and resulted in the solids content of the tank continuously building up and increasing. This fact, together with the depositing in the tank of a considerable quantity of paper lint picked up from the web by the doctor blade, caused a considerable change in the coating, when considering the beginning and end of an extended run. According to the present invention these objections and disadvantages are overcome, so that where relatively thick or quick-drying coatings are involved, an extremely uniform coated web product is obtained throughout a run. This is accomplished by the provision of an apparatus comprising a pick-up roller set over a tank containing the coating substance, the lower portion of the roller dipping into the coating substance so that a film of the latter is deposited on the roller as it turns. The top portion of the pick-up roller is engaged by a scraper blade having a surface inclined with respect to the horizontal and so arranged that the coating substance is caused to travel up the inclined surface. At the top of the inclined scraper surface a doctor or equalizer bar is provided, closely adjacent the edge of said surface, over which bar the continuous web of paper or other material is passed. As the pick-up roller is rotated and the coating substance is caused to adhere to it, and to travel up the inclined surface of the scraper blade it collects or gathers at the top of the blade and at the equalizer bar there located, and is applied to the underside of the continuous web.

' By adjusting the amount of inclination of the scraper bladeto suit the viscosity and other properties of the coating substance, all of said substance which is picked by the blade may be made to travel the full length of the blade and be deposited on the undersurface of the web as the coating thereof. Therefore no coating substance is at any time returned from the paper to the tank to'increase the concentration of solids therein or otherwise eii'ect the composition of the coating substance, nor is paper lint or other foreign matter deposited in the tank tpphange the characteristics of the coating dope, As' a consequence, an extremely uniform coating is applied to the web, and the said coating may have a relatively substantial thickness or be relatively quick-drying without adversely eilecting the uniformity thereof.

The apparatus by which the coating is applied, in accordance with this invention, is preferably so organized that the portion of the web in contact with the gathered coating substance is of extremely short length,,thereby to minimize the tendency for the vehicle of the coating substance to be absorbed by the web and cause a concentration of solids on the web surface prior to the equalizing of the coating by the doctor bar.

By virtue of the adjustable inclination of the scraper blade, coating dope having different degrees of viscosity may be effectively handled and applied-to a continuous web to produce an extremely uniform coating thereon. Furthermore the adjustment of the inclination of the scraper blade provides for maintenance of the desirable narrow contact band between the web'and the coating material, regardless of the viscosity of the particular coating being applied.

Other features and advantages will hereinafter appear.

In the accompanying drawings:

Figure 1 is a plan view of the improved coating apparatus made according to the invention and illustrating one embodiment thereof, and

Fig. 2 is a vertical sectional view taken on line 2-2 of Fig. 1. n

As shown, the apparatus comprises a frame I!) having spaced side members I I and having spaced brackets 12 extending horizontally from corresponding edges of the members H for supporting a roll or supply l3 of paper web l4 or the like. The web of paper l4 passes between the side members II and over an equalizer or doctor bar I5 to rewind roll l6 supported on a conventional rewind stand I I. if It is to be understood that the web of paper I4 is tensioned between the rolls I3 and i6 so as to be taut and present a smooth surface to the doctor bar I 5.

In accordance with the invention an improved and novel method and means is provided for applying coating substance to the web l4, in conjunction with the doctor bar l5, whereby no continually increasing excess of said substance is created at the point of application, requiring that it be returned to the supply tank, and whereby lint and other foreign matter from the web I4 is prevented from being deposited in the tank, to the end that a relatively thick coating, or a quickdrying coating or both may be applied to the web, and may have a high degree of uniformity Accordingly, referring to Fig, 2, there is pro- Y vided, mounted between the side members H of the frame III a pick-up roller l8, disposed over a tank or trough I9 containing coating substance or dope 20, the lower portion of said'roller dipping into the dope so that a film 2| of the dope caused to travel upwardly on said surface, and will collect or gather as shown at 24, Fig. 2. By this organization the underside of the web l4 may be efiectively coated with the coating dope 20 by virtue of its contact with the gathered dope at the top of the scraper blade 22 indicated at 24.

The doctor bar l5 preferably comprises a coil 25 of fine wire wound about a round bar 26 so that as the web l4 passes over the doctor bar only that amount of ink passing between the convolutions of the coil 25 will adhere to the web and spread by surface tension to provide the coating thereon. Only a small amount of the ink collected at the point 24 is thus allowed to pass the doctor bar l5 at any one time; however, the collected ink does not continue to build up to a greater and still greater mass, but instead passes by the bar l5 and coats the web I4 at the same rate as the film travels up the surface 23 of the scraper blade 22, and therefore only a narrow band of ink at the point 24 is maintained across the width of the web. By this organization the area of contact between the ink and web prior to the latter leaving the doctor bar I5 is held to a minimum, and relatively little absorption of vehicle and concentration of ink takes place in this area. Sufflcient ink will always be present at the point 24 for a continuous smooth coating of uniform thickness to be deposited on the web l4.

As shown, the blade 22 is provided with side plates 21 and a shaft 28 extending through the side plates to support the blade 22 between the side members I I of the frame It.

The doctor bar I5 is preferably connected to the blade 22 by fastening the ends of the bar 26 to the side plates 21, and the latter are provided with extended portions 29 adapted to engage the marginal edges of the web l4 and confine the ink to the underside of the web at the point 24.

To adjust for differences in the viscosity of various inks, so that a given ink will satisfactorily travel up the blade 22 to collect at the doctor bar IS. the blade 22 is adjustable in angular relation with the horizontal to present differently sloped surfaces 23 to the periphery of the pick-up roller l8. For ink that has great viscosity the blade 22 is made to be more upright, and for ink that has less viscosity the blade I9 is made to be more nearly horizontal. To accomplish this adjustment the shaft 28, supporting the blade 22 and the doctor bar I 5, has its ends carried in arcuate slots 30 provided in the side members ll of the frame It. Preferably the center of radius of the slots 30 is coincidental with the axis of the pick-up roller It so that when the shaft 23 is moved downward in the slots with the leading edge of the blade surface 23 engaging the periphery of the roller I8, the inclination of 4 the blade 22 will be decreased while its angle is deposited on the surface of the roller as the The upper edge of the surface 23 of the scraper blade extends closely adjacent the doctor bar l5, and may engage said bar, and when the pick-up roller I3 is turned in a counterclockwise direction as viewed in Fig. 2 the film 2| of coating dope will be deposited on the inclined surface 23 and At the top of the pick-up roller with respect to the tangent of the roller at the point of contact is maintained constant.

One end of the shaft" is provided with a flange 3| and the other end with a reduced threaded portion 32 having a washer 33 and a nut 34. The blade new be locked in the desired adjusted position by tightening the nut 34 so as to clamp the shaft 23 to the side members ll of the frame ll between the flange 3i and the washer 33.

As the ink is carried from the reservoir l9 and before it reaches the leading edge of the blade 22 a knife 35 provided on the frame l0 regulates the thickness of the ink on the periphery of the roller l3. For this purpose the knife 35 is positioned at the front of the roller l8 and is carried in a slot 33 of a bar 31 which is fastened to the side members ll of the frame In. The edge SI of the knife 35 is adapted to be regulated with respect to the periphery of the roller l8 by an adjusting screw 39 so that a correct amount of ink can be supplied to the blade 22.

Excess ink is wiped off the roller I! by the knife 35 and returned to the reservoir II.

To retain a uniform viscosity of the ink before and during the coating process the surfaces in .contact with theink are heated, and for this reason the reservoir l9, roller l8 and blade 22 are provided respectively with chambers 40, 4i and 42 connected by pipes 43 to a. source of heat.

The amount of ink fed to and traveling up the scraperd 22 may be made to equal the amount of ink coated on and retained by the 'web l4 in different ways. For example, the speed of the web l4 may be regulated, thereby to regulate the rate at which ink is removed from the scraper 22 at the top or delivering edge, For this purpose an electric motor 44 may be provided for driving the rewind roll IS, the speed of the motor being controlled by a rheostat 45 connected in the supply line 46 for the motor. Changing the setting of the rheostat 45 will change the speed of the rewind roll it and consequently the speed of the web l4.

Another way of balancing the amount of ink supplied to the scraper 22 at the lower or receiving edge thereof with the ink removed at the upper or delivering edge thereof would be by changing the speed of the pick-up roller i8. This may be accomplished by driving the roller from an electric motor 41 whose energization is controlled by a rheostat 48 connected in the supply line 49 for the motor. Further adjustments of course may be had by adjusting the knife and position of the scraper 22 as already mentioned above.

The organization and method as provided above is extremely simple and effective, and produces a highly desirable uniformity of coating on the web I4 even though the coating dope is quickdrying and the coating itself is of substantial thickness, and the apparatus is seen to be of simple and economical construction, and is reliable in operation with low maintenance costs.

.Variations and modifications may be made within the scope of this invention and portions of the improvements may be used without others.

I claim:

1. An apparatus for applying a viscous fluid coating substance to the surface of a web, comprising a member having an upwardly inclined surface on which said coating substance may travel from a receiving edge to a delivery edge thereof; means for continuously supplying predetermined amounts of coating substance to said surface at the receiving edge. whereby said substance is caused to continuously travel over said surface to the delivery edge thereon to form a bank of coating substance at said delivery edge for contact with, the surface of the web; means for feeding a web in one direction over said delivery edge of said surface; and an equalizer bar at and forming a substantial extension of said delivery edge as to engage both said web and that side of the bank of coating substance towards the retreating direction of the web.

2. An apparatus for applying a viscous fluid coating substance to the surface of a web, comprising a member having a stationary, upwardly inclined surface over which said coating substance may travel from a receiving edge to a higher delivery edge thereof; means, including a coating transfer means. located below said memher for continuously supplying predetermined amounts of coating substance to said surface at the receiving edge thereof, and for causing said substance to continuously travel over said surface to the delivery edge thereof, said member being 'above and having its lower end engaging the coating transfer means at substantially the highest point thereof; means for feeding a web past said delivery edge of the stationary surface; an equalizer bar located at and forming a substantial extension of said delivery edge and engageable with said web and coating substance picked up by the web for controlling the thickness of the coating on the web; and adjustable means mounting said member to change the angular position of the stationary surface thereof with respect to the horizontal and without substantially affecting the receiving relation of said receiving edge to said coating transfer means, thereby to control the rate of travel of the coating substance over said surface.

3. An apparatus for applying wax-base carbon ink to the surface of a web, comprising an elongate, stationary scraper having a flat surface upwardly inclined to the horizontal for traversal by said ink; means for adjustably mounting the scraper on the frame to alter the angular position of the flat surface thereof with respect to the horizontal; an equalizer bar extending along the upper edge of the flat scraper surface with the said surface being substantially tangential to said bar; a pick-up roller mounted for rotation below the scraper and engaged at substantially the highest point of the roller by the lower edge of the flat scraper surface regardless of the adjusted position of the scraper; means for rotating theroller; a tank below said roller for applying a film of ink, to the surface of the pick-up roller; means for regulating the thickness of the film of ink on the roller; and means for feeding a web over the equalizer bar and the upper edge of the flat scraper surface so as to approach said scraper from the direction in which said surface faces, rotation of said pick-up roller transferrin ink to the scraper and causing the ink to travel upward to the top edge of the scraper surface and to said web being coated with ink at said top edge, the rate of travel of ink over the flat scraper surface being controlled by the angular position of said surface.

4. Apparatus for coating the underside of a paper web with wax-base carbon ink comprising an upwardly inclined plate on and up which ink may travel from a receiving edge to a delivery edge where it forms a bank and is contacted and picked up by the paper web as it travels over said delivery edge; an equalizer bar at and forming a substantial extension of the delivery edge of the plate for controlling the thickness of the coating of ink picked up by the paper web and spreading the same; an ink supply trough; a ductor roller rotating in said trough and engaged by the receivin edg of the plate at substantially the highest point of the roller whereby ink on said ductor roller is transferred to the plate and propelled up the plate to the delivery edge thereof and against the traveling paper to be coated; means for rotating said roller; and means to control the quantity of ink delivered to the delivery edge of said plate to the amount which the paper web picks up as it travels whereby no ink coming in contact with the paper web is returned to the ink supply trough.

5. Apparatus for coating the underside of a paper web with wax-base carbon ink comprising an upwardly lnclinedplate on and up which ink may travel from a receiving edge to a delivery edge where it formsa bank and is contacted and picked up by the paper web as it travels over said delivery edge; an equalizer bar at and forming a substantial extension of the delivery edge of the plate and engaging the bank to control the thickness of the coating of ink picked up by the paper web and spread the same; an ink supply trough; and a ductor roller rotating in said trough, said plate having the receiving edge thereof engaging the ductor roller and the delivery edge positioned above the highest point of said ductor roller whereby ink on said ductor roller is transferred to the plate and propelled up the plate to the delivery edge thereof and against the traveling paper to be coated.

DOUGLAS A. NEWMAN.

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